It remains the case that tooth brushing generally involves a process of squeezing toothpaste onto a toothbrush head prior to brushing. It has long been recognised that greater convenience could be afforded by providing a toothbrush with an in-built reservoir from which the dentifrice is dispensed during brushing, either intermittently or continuously. Such an approach can also facilitate a more balanced delivery of dentifrice throughout the brushing process.
Such an idea is not new. For example, U.S. Pat. No. 730,040 discloses a toothbrush having a simple receptacle for feeding a liquid dentifrice into the bristles of the brush. U.S. Pat. No. 3,217,720 describes a toothbrush that can contain more than one liquid dentifrice container, the container(s) being separate items that are loaded into the toothbrush body. U.S. Pat. No. 5,909,977 discloses a dentifrice dispensing toothbrush utilizing a refillable cartridge for storing dentifrice material and a compressible elastic button for pumping dentifrice material to the brush head. An extension of the dispensing toothbrush concept into the realm of powered toothbrushes is disclosed in U.S. Pat. No. 5,309,590, which describes a brush having hollow bristles through which the dentifrice flows. In addition to the better cleaning that electric toothbrushes generally provide, electric toothbrushes offer further particular advantages for dispensing toothbrushes, such as the possibility of using a microprocessor to control dispensing or using the power source to pump dentifrice to the toothbrush head. WO 02/41801 describes an electrically powered, dispensing toothbrush, comprising more than one product reservoir, which can selectively dispense two or more products simultaneously or sequentially. The dispensing can be under the control of a microprocessor. US 2003/0221270 and U.S. Pat. No. 6,957,925 both describe powered brushes where the power is used to pump dentifrice to the toothbrush head as well as to drive a moving brush head. The former document describes a brush with a replaceable reservoir and the latter a brush with a permanent, refillable reservoir.
Despite the obvious appeal of dispensing or ‘reservoir’ toothbrushes, and the many thousands of designs for them that have been suggested through the patent literature over several decades, they have not yet become commercially successful on a large scale. U.S. Pat. No. 5,918,995 discloses a brush with an integral refillable container from which dentifrice can be pumped to the brush head by a manually operated diaphragm pump. A brush as described in the patent was commercialised by Pump&Brush Finland Oy but has not received broad scale distribution. The Fresh&GO™ toothbrush was launched in the US in 2000. It is a disposable toothbrush, aimed at travelers, and as a result is of limited appeal. In October 2004, the ‘IntelliClean® System’ was launched onto the US market by an alliance of Royal Philips Electronics and The Procter & Gamble Company. This electrically powered ‘sonic’ toothbrush comprises a replaceable flexible sachet from which dentifrice can be pumped to the brush head by a manually operated diaphragm pump. Its long term market success remains to be demonstrated.
A substantial technical problem that all such brushes have to confront is that of reliably providing for the dentifrice to be easily transported from the in-built reservoir to the toothbrush head. Typically the dentifrice has to be carried through a relatively long (compared to the neck of a toothpaste tube) but narrow conduit whose dimensions are constrained by the toothbrush neck. The problem is even more acute in the case of an electrically driven brush head because the brush neck also needs to accommodate the drive train for the brush head. Further, the need for the handle to accommodate a motor and batteries has led many designs to require a long dentifrice supply conduit from the reservoir to the brush head, which further exacerbates the problem of transporting the dentifrice to the brush head. In practice this has often meant that dentifrice for dispensing brushes has had to be formulated at a lower viscosity than is typical for many commercial pastes. This, in particular, imposes a restriction on the solids content of the dentifrice and constrains the formulator of the dentifrice. Many desirable toothpaste ingredients are best used in solid form for reasons of either stability (for materials that might be hydrolysed in solution) or efficacy (such as an abrasive). A diaphragm pump sized for a toothbrush has difficulty in sucking replacement dentifrice from a reservoir if the dentifrice is of high viscosity. An alternative approach is to push the dentifrice to the bristles by using, for example, a plunger or a screw fed piston. See U.S. Pat. No. 6,056,466 for an example of this kind. The transport mechanism is normally provided at the handle end of the brush, which is not so easy to use during brushing as a push button near the neck. Some toothbrushes have addressed this by providing a neck activation feature for a base fed piston, see e.g. U.S. Pat. No. 6,142,694, which describes the Fresh&GO™ toothbrush mentioned above, and the above-mentioned U.S. Pat. No. 6,957,925 which uses an electrically operated screw-fed piston. Whilst these approaches address the problem of ease of activation, they do so at the expense of increased mechanical complexity, raising questions over the long term reliability of the brushes.
The present inventor has now developed a dispensing toothbrush which provides for convenient operation, low mechanical complexity and ease of replacement of the dentifrice reservoir.
An important feature of the brush is a replaceable pressurised reservoir of the bag in can variety, the bag being charged before use with a dentifrice and the can containing propellant between the bag and the can.
The use of propellants for dispensing dentifrice, even in a dispensing brush, is not new. U.S. Pat. No. 3,825,354 describes a toothbrush with a hollow head into which toothpaste can be injected from a separate aerosol can using a special adapter. Each of the patent documents U.S. Pat. Nos. 2,987,743, 3,592,551, 3,606,555, 3,868,188, 3,910,706, 3,937,582, WO 86/02534, EP 437706 and GB 2,313,774 describes a manual toothbrush or similar oral applicator whose handle comprises a container, in some instances a replaceable cartridge, containing a mixture of toothpaste and propellant. The propellant pressure dispenses the paste through a conduit to the brush head. Disadvantages of incorporating the propellant into the paste include i) the paste foaming as the pressure is released; ii) as the dentifrice reservoir progressively empties the density of the paste drops and the amount of paste delivered does not remain uniform; iii) remaining dentifrice may not contain sufficient propellant for it to be properly dispensed; and iv) when the propellant is in the same reservoir, dispensing of the paset from the reservoir typically only works well when the reservoir is in a single orientation. In U.S. Pat. No. 3,937,235 the pressure on the dentifrice is provided by a separate flexible bag containing a Freon® propellant. This document envisages the entire handle being replaced when the toothpaste is exhausted. In U.S. Pat. No. 5,407,287 the pressure on the dentifrice is provided by a propellant driven piston. FR 2 484 960 describes a toothpaste container of a ‘bag-in-can’ type of construction from which the dentifrice can be delivered as a spray.
None of the disclosures of propellant based dentifrice dispensers mentioned above provides a structure suitable for an electric brush. The present invention provides such a brush, with many advantageous features, as described herein. In particular, the invention provides for an electrically driven toothbrush utilizing replaceable bag-in-can aerosol cartridges within a compact brush structure which, amongst other advantages, is easily used and maintained by an end consumer and can be used in any orientation.